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rfc:rfc5328

Network Working Group A. Adolf Request for Comments: 5328 Micronas GmbH Category: Informational P. MacAvock

                                                           DVB Project
                                                        September 2008
            A Uniform Resource Name (URN) Namespace for
            the Digital Video Broadcasting Project (DVB)

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Abstract

 This document describes a Uniform Resource Name (URN) namespace for
 the Digital Video Broadcasting Project (DVB) for naming persistent
 resources defined within DVB standards.  Example resources include
 technical documents and specifications, eXtensible Markup Language
 (XML) Schemas, classification schemes, XML Document Type Definitions
 (DTDs), namespaces, style sheets, media assets, and other types of
 resources produced or managed by DVB.

Table of Contents

 1. Introduction ....................................................2
 2. Specification Template ..........................................2
 3. Examples ........................................................4
 4. Namespace Considerations ........................................4
 5. Community Considerations ........................................7
 6. Security Considerations .........................................9
 7. IANA Considerations .............................................9
 8. References .....................................................10
    8.1. Normative References ......................................10
    8.2. Informative References ....................................11

Adolf & MacAvock Informational [Page 1] RFC 5328 DVB URN September 2008

1. Introduction

 The Digital Video Broadcasting Project (DVB) is an industry-led
 consortium of over 270 broadcasters, manufacturers, network
 operators, software developers, regulatory bodies and others in over
 35 countries committed to designing global standards for the global
 delivery of digital television and data services.  Services using DVB
 standards are available on every continent with a total of more than
 100 million DVB receivers already deployed.
 DVB would like to assign unique, permanent, location-independent
 names based on URNs for some resources it produces or manages.  These
 URNs will be constructed according to the URN syntax defined in
 [RFC2141].
 This namespace specification is for a formal namespace to be
 registered according to the procedures set forth in [RFC3406].

2. Specification Template

 This section provides the information required to register a formal
 namespace according to the registration procedure defined in
 [RFC3406].  The URNs conform to the syntax defined in [RFC2141].
 Namespace ID:
    "dvb"
 Registration Information:
    Version: 1
    Date: 2007-02-28
 Declared registrant of the namespace:
    Name:           Peter MacAvock
    Title:          Executive Director, DVB Project Office
    Affiliation:    DVB Digital Video Broadcasting
    Address:        Ancienne Route 17a
                    CH-1218 Geneva
                    SWITZERLAND
    Phone:          +41 22 717 2719
    Email:          macavock@dvb.org

Adolf & MacAvock Informational [Page 2] RFC 5328 DVB URN September 2008

 Declaration of structure:
    URNs assigned by DVB will have the following hierarchical
    structure based on the organizational structure of the DVB
    standards:
       urn:dvb:<NSS>
    where the syntax of "<NSS>" is specified in Section 2.2 of the URN
    Syntax requirements ([RFC2141]).
    The individual URNs will be assigned by DVB through the process of
    development of DVB standards.
 Relevant ancillary documentation:
    None
 Identifier uniqueness considerations:
    DVB will establish unique identifiers as appropriate.
    Uniqueness is guaranteed as DVB ensures through its
    standardization process that an assigned string is never
    reassigned.
 Identifier persistence considerations:
    DVB is committed to maintaining the accessibility and persistence
    of all resources that are officially assigned URNs by the
    organization.
 Process of identifier assignment:
    Assignment is limited to DVB and those authorities that are
    specifically designated by DVB.  DVB may designate portions of its
    namespace for assignment by other parties under its regime.
 Process of identifier resolution:
    DVB will develop and maintain "URN catalogues" that map all
    assigned URNs to Uniform Resource Locators (URLs) specifically to
    enable Web-based resolution of named resources.  In the future, an
    interactive online resolution system may be developed to automate
    this process.  The latest information about DVB-defined metadata
    can always be found on the DVB website at:
       http://www.dvb.org/metadata

Adolf & MacAvock Informational [Page 3] RFC 5328 DVB URN September 2008

    DVB will authorize additional resolution services as appropriate
    and in-line with the DVB standardization process.
 Rules for Lexical Equivalence:
    The "<NSS>" is case insensitive.
 Conformance with URN Syntax:
    No special considerations.
 Validation mechanism:
    None specified.  DVB will develop and maintain URN catalogues.
    The presence of a URN in a catalogue indicates that it is valid.
 Scope:
    Global

3. Examples

 The following examples are not guaranteed to be real.  They are
 presented for pedagogical reasons only.
    urn:dvb:ipdc:esg:2005
    urn:dvb:cs:ZappingTypeCS:2001

4. Namespace Considerations

 The urn:dvb namespace is used to identify metadata that is defined by
 DVB and describes DVB multimedia and interactive services.  The
 registration of urn:dvb as a formal namespace enables the use and
 referencing of DVB XML fragments in other standards worldwide and
 enables those standards to leverage and build upon publicly available
 DVB metadata schemas and fragments.
 These URNs are used to refer to, in conjunction with, and as part of
 commercial or public multimedia broadcast services.  In most markets,
 these are under the control of a national regulator.  So if a
 particular market chooses to use DVB services, in general, the
 regulator imposes compliance with the relevant DVB specifications to
 ensure interoperability and open competition in the marketplace.

Adolf & MacAvock Informational [Page 4] RFC 5328 DVB URN September 2008

 URN assignment procedures:
    The individual URNs shall be assigned through the process of
    development of DVB standards by the Digital Video Broadcasting
    Project (DVB).  The latest information about DVB defined metadata
    can always be found at the owner's website at:
    http://www.dvb.org/metadata
 URN resolution/delegation:
    The resolution and delegation shall be determined through the
    process of development of DVB standards by the Digital Video
    Broadcasting Project (DVB).
    Since the implementations envisaged cover a wide range of devices
    with quite different access methods and capabilities, no single
    resolution or delegation mechanism can be referenced in this
    document.
    Currently, 2 client system classes are covered by DVB
    specifications:
     o  A broadcast set-top box that only has a unidirectional,
        receive-only connection.  Hence, all DVB URNs need to be
        resolvable from the service discovery information received in
        the broadcast stream.
     o  A "home network end device" (HNED) that could be an IPTV set-
        top box, networked TV, or personal digital recorder with an
        Ethernet or Wireless Local Area Network (WLAN) connection to a
        home gateway device.
    Further device classes will be addressed as DVB standardization
    progresses.  The urn:dvb URNs must however remain valid.  DVB will
    define appropriate resolution/delegation mechanisms to ensure that
    DVB URNs remain valid for those new device classes as well.
    For the two above example device classes, 3 ways of conveying such
    resolution information are currently defined by DVB:
    o  Repeated, cyclic transmission of Resolution Authority Records
       (RAR) and Resolution Records (RR) as auxiliary data in digital
       TV broadcast streams over satellite, cable, or terrestrial
       transmissions according to [EN300468], [EN301192], and
       [TS102323].

Adolf & MacAvock Informational [Page 5] RFC 5328 DVB URN September 2008

    o  Repeated, cyclic multicast transmission of Resolution Records
       (RR) via the DVBSTP protocol according to [TS102034].
    o  Unicast delivery of Resolution Records (RR) in response to HTTP
       "GET /dvb/sdns" requests according to [TS102034].
 Type of resources to be identified:
    Types of resources to be identified include XML schema definition
    files, classification schemes, and identification systems defined
    and openly published by DVB.  These resources being identified
    constitute a metadata system to describe digital multimedia
    broadcast services or content conveyed as part of such services.
    The latest DVB defined metadata can always be found at:
    http://www.dvb.org/metadata
    These metadata definitions are not entirely usable without
    knowledge of the DVB specifications listed in the Normative
    References section.  To make them generally useful for client
    platforms typically found in computer network environments today,
    XSLT transformations to HTML, or other common formats would be
    needed to enable rendering in a standard web browser.  On the
    other hand, it is expected that with the increasing overlap
    between the computer and multimedia worlds - e.g., with the
    forthcoming DVB file format definition - DVB metadata formats will
    get adopted in player implementations on PC platforms as well.
 Type of services to be supported:
    Types of services supported include controlled term lookup in
    classification schemes and resolution of ids in identification
    systems.
    Concrete examples of these services include digital television
    services, (near) video on-demand services, and digital radio sound
    services.  Another example is interactive multimedia applications
    which are tied to audiovisual content.
    This might, e.g., be a quiz show where viewers can compete against
    the contestants on the show by picking multiple-choice answers
    with their remote control.  These end-user services are enabled by
    the metadata defined under the urn:dvb namespace.
    Another example is the web-portal site for the video-on-demand
    offering of an ISP.  The portal pages are likely to describe the
    content in terms of title, genre, parental guidance, cast, etc.
    The ISP might either publish the DVB format description on their

Adolf & MacAvock Informational [Page 6] RFC 5328 DVB URN September 2008

    web-portal site directly, or develop an XSLT transformation to
    obtain an HTML incarnation of the data.  In either case, a client
    device (in this example the home gateway or the ISP's web portal)
    will need to be able to resolve references to the urn:dvb
    namespace.  Describing multimedia content in DVB format is a
    likely choice since it provides rich information specially
    tailored to multimedia applications like television, movies,
    music, etc.  Furthermore, the DVB content descriptions for
    consumer terminals are, of course, compatible with the DVB
    Portable Content Format (PCF, defined in ETSI TS 102 523), which
    is used in content production environments so that propagation of
    content descriptions along the entire production chain is easily
    achieved.

5. Community Considerations

 With the digitization of the audiovisual broadcasting technologies,
 television receiver platforms have become quite similar to personal
 computer equipment in terms of performance, resources, and
 interfaces.  Hence, cross-use of content from the respective other
 platform (i.e., TV and PC) becomes interesting to consumers and
 service providers alike.  Web pages can for instance today be viewed
 on a general purpose computer, a set-top box, and a mobile phone just
 the same.  Audio/video broadcasting services are arriving on mobile
 phones today ("mobile TV"), and efforts are clearly visible to bring
 such services to personal computer platforms as well ("IPTV").
 Hence, cross-linking between these two domains, the Internet/personal
 computer domain and the TV/broadcast domain is called for.  Linking
 from broadcast domain metadata to Internet-based services is already
 enabled through the various URN and URI schemes established in the
 relevant DVB standards ([EN300468], [TS102323], and [TS102034]).
 Linking from Internet/web resources to DVB multimedia services is not
 yet possible in a well-defined way.  Thus, a URN scheme is proposed
 for DVB defined metadata describing DVB services.  As DVB issues its
 publications as international standards and has a well-defined
 compliance regime, this request is for a formal namespace.
 Open assignment and use of identifiers within the namespace:
    With on-going development of DVB standards, DVB will establish
    requirements for assignment and use of identifiers within the DVB
    namespace.  Current identifier assignments can be inferred from
    the relevant DVB standards and from http://www.dvb.org/metadata.

Adolf & MacAvock Informational [Page 7] RFC 5328 DVB URN September 2008

 Considerations for resolution server software:
    With on-going development of DVB standards, DVB will establish
    requirements and seek candidates for operating resolution servers
    as appropriate.
    Sources for resolution information can either be stand-alone
    resolution services, which are announced as part of the Service
    Discovery and Selection (SD&S), or data conveyed as part of the
    SD&S information itself.  To boot-strap the resolution process, a
    DVB client hence needs to discover an entry point (or set of) from
    which to obtain an initial Service Discovery and Selection XML
    record.
    By default, the actual service discovery information is provided
    on the IANA registered well-known port dvbservdsc (port number
    3937) via tcp and udp (see http://www.iana.org/assignments/port-
    numbers) on the IANA registered well-known multicast addresses
    224.0.23.14 (DvbServDisc on IPv4) and FF0X:0:0:0:0:0:0:12D
    (DvbServDisc on IPv6).
    As set forth in [TS102034], a list of non-default Service
    Discovery and Selection (SD&S) entry points addresses may also be
    provided via DNS based on the service location resource record
    (SRV RR) [RFC2782].  The service name for DVB services is
    "_dvbservdsc", the protocol may be tcp or udp, while the rest of
    the name is the domain name maintained by DVB for service
    discovery.  This domain name is set to "services.dvb.org".  The
    DVB organization will maintain the services.dvb.org domain name
    for service discovery, and new service providers should register
    with DVB to add them to the DNS SRV list.
 Considerations for resolution client software:
    With on-going development of DVB standards, DVB members will
    develop software implementations of its standards for various
    platforms.  Today, these platforms typically include Open Source-
    based platforms such as Linux.
    To resolve a urn:dvb name, a client needs to retrieve Service
    Discovery and Selection (SD&S) data since this either directly
    contains resolution data, or lists stand-alone resolution services
    from which Resolution Authority Records (RAR) can be retrieved.
    To obtain the initial Service Discovery and Selection (SD&S) XML
    record, a client must by default first join the IANA registered
    well-known multicast addresses 224.0.23.14 (DvbServDisc on IPv4)
    and/or FF0X:0:0:0:0:0:0:12D (DvbServDisc on IPv6) and try to

Adolf & MacAvock Informational [Page 8] RFC 5328 DVB URN September 2008

    obtain a boot-strap record from the IANA registered well-known
    port dvbservdsc (port number 3937) via tcp and udp (see
    http://www.iana.org/assignments/port-numbers).
    To discover non-default entry points addresses, [TS102034] defines
    that a list of Service Discovery and Selection (SD&S) entry points
    addresses may be acquired via DNS according to the service
    location resource record (SRV RR) [RFC2782].  The service name is
    "_dvbservdsc"; the protocol may be tcp or udp, while the rest of
    the name is the domain name maintained by DVB for service
    discovery.  This domain name is set to "services.dvb.org".  So the
    lookup shall be either "_dvbservdsc._tcp.services.dvb.org" or
    "_dvbservdsc._udp.services.dvb.org".  This requires that the
    terminal support an SRV cognizant DNS client and in a way
    according to the specification in [RFC2782].  The DVB organization
    will maintain the services.dvb.org domain name for service
    discovery.  HTTP servers will be found via the tcp protocol method
    whilst the multicast addresses will be found via the udp protocol
    method.

6. Security Considerations

 There are no additional security considerations other than those
 normally associated with the use and resolution of URNs in general,
 which are described in [RFC1737], [RFC2141], and [RFC3406].
 This document registers a namespace for URNs.  DVB may assign special
 meaning to certain of the characters of the Namespace Specific String
 in its specifications.  Any security consideration resulting from
 such assignment is outside the scope of this document.
 When URNs are resolved, i.e., translated from names to locations, the
 way the locations are used or accessed may require the resources to
 be authenticated.  The information about the authentication of either
 the name or the resource to which it refers should be carried by
 separate information passed along with the URN rather than in the URN
 itself.  The design of such resolution mechanisms by DVB for DVB URNs
 is guided by [RFC2276] and such mechanisms will be published as DVB
 specifications.

7. IANA Considerations

 This document defines a URN NID registration of "dvb".  IANA has
 registered "dvb" in the URN Namespaces registry.

Adolf & MacAvock Informational [Page 9] RFC 5328 DVB URN September 2008

8. References

 Note: The ETSI specifications listed below - as all ETSI standards -
       are available to the general public free of charge.  They are
       accessible by going to http://www.etsi.org and visiting the
       standards download page.  Select "Standards" from the
       navigation bar at the top, then choose "Download ETSI
       Standards" in the contents box on the left.  A "Publications
       Download Area" link occurs at the top of the body text).  The
       direct link to the downloads page is
       http://pda.etsi.org/pda/queryform.asp.  When clicking on the
       download link on the search results page, an email address is
       requested for the PDF download.  As being free-of-charge is
       funded by the European Commission, the email addresses are
       collected for statistical purposes only to demonstrate benefit
       to the general public.
       The ETSI specifications are normative references since the URNs
       are used to refer to, in conjunction with, and as part of
       commercial or public multimedia broadcast services.  In most
       markets, these are under the control of a national regulator.
       So if a particular market chooses to use DVB services, in
       general, the regulator imposes compliance with the relevant DVB
       specifications to ensure interoperability and open competition
       in the marketplace.  Some of the specifications also have "EN"
       status, which means that the European Commission has overridden
       any national regulations by mandating that if any commercial
       service is rolled out in Europe in the respective area, it must
       comply with the relevant DVB EN specification(s).  Apart from
       those legal implications, DVB has become a brand to which
       consumers link certain expectations with regard to the level of
       service and interoperability.  Of course, DVB wants to help
       manufacturers meeting those expectations by fostering
       interoperability.

8.1. Normative References

 [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.
 [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
            "Uniform Resource Names (URN) Namespace Definition
            Mechanisms", BCP 66, RFC 3406, October 2002.
 [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
            specifying the location of services (DNS SRV)", RFC 2782,
            February 2000.

Adolf & MacAvock Informational [Page 10] RFC 5328 DVB URN September 2008

 [EN300468] European Telecommunications Standards Institute (ETSI),
            "Digital Video Broadcasting (DVB); Specification for
            Service Information (SI) in DVB systems", October 2007.
 [EN301192] European Telecommunications Standards Institute (ETSI),
            "Digital Video Broadcasting (DVB); DVB specification for
            data broadcasting", November 2004.
 [TS102323] European Telecommunications Standards Institute (ETSI),
            "Digital Video Broadcasting (DVB); Carriage and signalling
            of TV-Anytime information in DVB transport streams",
            November 2005.
 [TS102034] European Telecommunications Standards Institute (ETSI),
            "Digital Video Broadcasting (DVB); Transport of MPEG-2 TS
            Based DVB Services over IP Based Networks", October 2007.

8.2. Informative References

 [RFC1737]  Sollins, K. and L. Masinter, "Functional Requirements for
            Uniform Resource Names", RFC 1737, December 1994.
 [RFC2276]  Sollins, K., "Architectural Principles of Uniform Resource
            Name Resolution", RFC 2276, January 1998.

Authors' Addresses

 Alexander Adolf
 Micronas GmbH
 Frankenthalerstrasse 2
 D-81539 Munich
 GERMANY
 Tel: +49 89 54845 7203
 Fax: +49 89 54845 7900
 EMail: alexander.adolf@micronas.com
 Peter MacAvock
 DVB Digital Video Broadcasting
 Ancienne Route 17a
 CH-1218 Geneva
 SWITZERLAND
 Tel: +41 22 717 2717
 EMail: macavock@dvb.org

Adolf & MacAvock Informational [Page 11] RFC 5328 DVB URN September 2008

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 contained in BCP 78, and except as set forth therein, the authors
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Adolf & MacAvock Informational [Page 12]

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